Interface FileVisitor<T>
- Type Parameters:
T
- the type of file/directory
- All Known Implementing Classes:
SimpleFileVisitor
public interface FileVisitor<T>
A visitor of files. An implementation of this interface is provided to the
Files.walkFileTree
methods to visit each file in
a file tree.
Usage Examples: Suppose we want to delete a file tree. In that case, each directory should be deleted after the entries in the directory are deleted.
Path start = ...
Files.walkFileTree(start, new SimpleFileVisitor<Path>() {
@Override
public FileVisitResult visitFile(Path file, BasicFileAttributes attrs)
throws IOException
{
Files.delete(file);
return FileVisitResult.CONTINUE;
}
@Override
public FileVisitResult postVisitDirectory(Path dir, IOException e)
throws IOException
{
if (e == null) {
Files.delete(dir);
return FileVisitResult.CONTINUE;
} else {
// directory iteration failed
throw e;
}
}
});
Furthermore, suppose we want to copy a file tree to a target location. In that case, symbolic links should be followed and the target directory should be created before the entries in the directory are copied.
final Path source = ...
final Path target = ...
Files.walkFileTree(source, EnumSet.of(FileVisitOption.FOLLOW_LINKS), Integer.MAX_VALUE,
new SimpleFileVisitor<Path>() {
@Override
public FileVisitResult preVisitDirectory(Path dir, BasicFileAttributes attrs)
throws IOException
{
Path targetdir = target.resolve(source.relativize(dir));
try {
Files.copy(dir, targetdir);
} catch (FileAlreadyExistsException e) {
if (!Files.isDirectory(targetdir))
throw e;
}
return CONTINUE;
}
@Override
public FileVisitResult visitFile(Path file, BasicFileAttributes attrs)
throws IOException
{
Files.copy(file, target.resolve(source.relativize(file)));
return CONTINUE;
}
});
- Since:
- 1.7
-
Method Summary
Modifier and TypeMethodDescriptionpostVisitDirectory
(T dir, IOException exc) Invoked for a directory after entries in the directory, and all of their descendants, have been visited.preVisitDirectory
(T dir, BasicFileAttributes attrs) Invoked for a directory before entries in the directory are visited.visitFile
(T file, BasicFileAttributes attrs) Invoked for a file in a directory.visitFileFailed
(T file, IOException exc) Invoked for a file that could not be visited.
-
Method Details
-
preVisitDirectory
Invoked for a directory before entries in the directory are visited.If this method returns
CONTINUE
, then entries in the directory are visited. If this method returnsSKIP_SUBTREE
orSKIP_SIBLINGS
then entries in the directory (and any descendants) will not be visited.- Parameters:
dir
- a reference to the directoryattrs
- the directory's basic attributes- Returns:
- the visit result
- Throws:
IOException
- if an I/O error occurs
-
visitFile
Invoked for a file in a directory.- Parameters:
file
- a reference to the fileattrs
- the file's basic attributes- Returns:
- the visit result
- Throws:
IOException
- if an I/O error occurs
-
visitFileFailed
Invoked for a file that could not be visited. This method is invoked if the file's attributes could not be read, the file is a directory that could not be opened, and other reasons.- Parameters:
file
- a reference to the fileexc
- the I/O exception that prevented the file from being visited- Returns:
- the visit result
- Throws:
IOException
- if an I/O error occurs
-
postVisitDirectory
Invoked for a directory after entries in the directory, and all of their descendants, have been visited. This method is also invoked when iteration of the directory completes prematurely (by avisitFile
method returningSKIP_SIBLINGS
, or an I/O error when iterating over the directory).- Parameters:
dir
- a reference to the directoryexc
-null
if the iteration of the directory completes without an error; otherwise the I/O exception that caused the iteration of the directory to complete prematurely- Returns:
- the visit result
- Throws:
IOException
- if an I/O error occurs
-